Modern computer systems may be composed of a number of processors. These processors may be configured with multiple processors on one integrated circuit. Alternately, they may be configured on multiple networked computers. Tasks may be allocated between processors by an operating system or a separate computer program. Each processor generates heat. That heat generation is increased as more processes run, and as those processes run at faster speeds. Excess heat can degrade the performance of an individual processor, or even cause failure of that device. If the temperature distribution of the various processors is uneven, and some of them exceed the threshold while others are far below the threshold, the speed of those overheated processors is throttled and the performance of the entire system goes down. Other processors that are not overheated may be underutilized and the overall system performance may degrade. On the other hand, if the temperature of all CPU is kept below the threshold, all CPU's can keep running at full speed. Therefore, it is advantageous to manage the heat in a multi-processor computer system.
Some modern processors are designed with electronic sensors resident in the same integrated circuit chip as the central processing unit (“CPU”) of the processor for measuring the temperature at or near the CPU. Alternately, a circuit board may contain a temperature sensor located physically near the processor if one is not resident in the same chip. Controlling mechanisms, either in operating system software or elsewhere may utilize this temperature data or act on the computer system or individual processors to minimize overheating of either individual processors or the overall system. In some modern processors, the temperature sensor may be passive, as in the case of a resistor, whose electrical resistivity varies with temperature. Alternately, the processor chip may include an active sensor, which can send a signal when the chip temperature exceeds a predetermined value.
While generation of heat is due to processor activity, dissipation of that heat may be influenced by many factors. For example, the physical mounting of a processor may affect the rate at which heat is dissipated. Similarly, airflow around the processor may affect the heat dissipation rate. Greater airflow can result in faster heat dissipation, while the reverse may be true also. One approach to thermal management involves managing tasks assigned to processors.